In subsurface and sub-seabed drilling operations, knowledge of the magnetic field direction and strength is important in determining drilling direction. The earth's magnetic field (geomagnetic field) direction and strength differs based on location, time, and the total magnetic field measured at any given point is additionally affected by any local formations and anomalies that include magnetic material. A global magnetic model based on a survey may be used as a reference, but this survey may not be updated for years. Thus, an aeromagnetic survey may be conducted in the specific area where drilling is to occur. The aeromagnetic survey involves using a magnetometer on or towed by an aircraft and results in an aeromagnetic survey map that may be more up-to-date than the global magnetic model.